She isnt that bad but she isnt good either. Its not fair for her to stay in this state just because her full Q does good damage early game. Why? because the Q is difficult to hit the whole volley so the excuse is void. Minions kills Q damage.
if anything they should buff her Q, in fact, all her skills, but in functionality not in damage.
Well, they can do something about WG Q, is too weak. Maybe increase Q range on WG? at least to poke from a safe distance.
Reduce mana costs of W and E,
improve cooldown and lenght of ult at Lvl 1 (both are dreadful),
and last but not least, IMPROVE HER PASSIVE. Is lackluster, situational and weird.
And do not underestimate taliyah support, she can set up kills really good. She is not awesome, as all-in champs and super pokers WILL wrck her, but she is not a pushover either.